Soil Biology and Ecology
42 | Unit 2.3
Assessment Questions Key
Assessment Questions Key
- what is soil?
• An ecological system consisting of inorganic
minerals (sand, silt, clay, and nutrients), pore
spaces, water, gases, organic matter, living
organisms, and plants
- what forms of life exist in soil ecosystems?
• Bacteria, fungi, actinomycetes, millipedes,
isopods, mollusks, insects, insect larvae,
worms and many small vertebrate animals
such as gophers, ground squirrels, moles, etc.
- How would you define a “healthy” agricultural
soil?
• A soil with a set of desirable physical and
chemical properties which has the capacity
to sustain biological productivity, maintain
environmental quality, and promote plant,
animal, and human health. This would
include many of the following general
characteristics:
a) adequate rooting depth for the crop(s) to be
grown
b) a 3–5% organic matter content
c) maintains stable soil aggregates
d) allows for rapid water infiltration without
soil erosion
e) a low bulk density (good structure with
minimal compaction)
f) pH between 6 and 7
g) an extractable nutrient profile within the
optimal range of physiological tolerance for
the crops to be grown
h) good water holing capacity and well-drained
i) high soil biological diversity and activity (soil
respiration)
j) adequate supplies of labile organic matter
with potentially mineralizable nitrogen
k) seasonal soil temperatures from 60–85ºF
4) what is a soil food web?
• The entire assemblage of soil organisms
(producers, consumers and decomposers)
in a soil ecosystem interacting among and
between trophic levels5) what might be some negative effects of
the long-term practice of monoculture
cropping and the use of synthetic chemical
fertilizer and pest control agents on the soil
ecosystem?
• Loss of SOM, reduction in soil aggregation,
reduction in nutrient- and water-holding
capacity, reduction in soil biological diversity
and activity, increased pest and disease
incidence